Microelectronic optical or photonic devices and systems including such devices may be used in a variety of applications. For example, optical devices are used ill passive displays such as liquid crystal displays (LCDs), high-definition television displays, modulators, filters, and the like.
In the case of LCD devices, an image is created by blocking or allowing transmission of light between a source and a screen or a display area. In particular, liquid crystal material, in conjunction with polarizing material and a mirror, is used to alter the transmission of light based on an applied electric filed. The applied electric field causes molecules within the liquid crystal material to align and form a quasi-crystalline structure, which in turn alters the reflectivity of the material. This change in reflectivity only persists for so long as the electric field is applied to the liquid crystal material. Thus, energy must be supplied to the liquid crystal material to maintain its orientation even when a displayed image is constant.
Use of liquid crystal material in connection with passive optical devices may be problematic in several regards. For example, as noted above, energy must be applied to the liquid crystal material to maintain information. In addition, the liquid crystal and a semiconductor circuit for operating the LCD are generally formed on separate substrates and must be mechanically and electrically coupled to each other. Coupling devices formed on separate substrates may be undesirably expensive and time consuming. Accordingly, improved photonic devices suitable for passive display applications and systems including the devices are desired.
Other applications where photonic devices are well suited include optical switches for use with routers in data communication systems. Presently, routers include optoelectronic components to convert optical information to electrical signals, components to filter and amplify the electronic signals, components to rout the electrical signals, and components to convert the electrical signals to optical information for further transmission. Use of electronic components to switch and rout optical information may be undesirable for several reason. For example, information integrity may be reduced by the conversion between optical and electrical signals, and the employment of electronic components may undesirably add to the cost and complexity of the switch and/or router. Improved methods and apparatus for switching and routing optical information are therefore desired.
Photonic devices may also include tunable grating devices for use as filters. In this case, the photonic device is coupled to a semiconductor circuit to operate the filter. Forming the photonic and electronic devices on separates substrate is undesirable for the reasons noted above. Accordingly, improved methods and apparatus for forming tunable grating devices and filters are desired.